Lipofectamine transfection problems

[kartikv]

Hey all,
I really need some help. Recently, I have been transfecting Mouse embryonic fibroblasts with MEFs and in the past I haven't had any significant problems, but this time for some reason, after the transfection is done and I change the media, next day, they form these ball of cells. But they aren't dead cells because they seem to not come off the plate - they are still adhering to the plate. If anyone has seen this before or has suggestions, that would be great.
Thanks,
kartikv